Igniter for rockets



1948' R. A. APPLETON ET AL 2,452,892

IGNITER FOR ROCKETS Filed May '7, 1947 Robert A gp latun El arencE N I-htkman Barnld F gnrk Patented Nov. 2, 1948 IGNITER FOR. ROCKETS Robert A. Appleton, Inyokern, Califl, Clarence N. Hickman, Jackson Heights, N. Y., and Garold F.

Bjork, Luke, Md., assignors to the United States of America as represented bythe Secretary of War Application May 7, 1947, Serial No. 746,548

3 Claims. 1

This invention relates to rockets and more particularly to a new and improved igniter for rockets.

The rockets to which this invention relates consist essentially of a cylindrical combustion chamber for containing a propellant which upon ignition and burning generates a hot gaseous fluid under pressure. The forward end of the motor combustion chamber is closed off and has secured thereto a suitable "pay-load? compartment. The rear of the chamber is provided with a Venturi-like nozzle which permits the gaseous combustion products to be discharged at a relatively high velocity. A cylindrical tube filled with a high explosive extends longitudinally and concentrically of the motor chamber. It is connected with the pay-load compartment and its purpose is the fragmentation of the motor chamber upon detonation of the pay-load.

The propellant consists of a plurality of cylindrical grains of singly-perforated double-base powder supportedon trap wires extending longitudinally of the chamber, and prior to our invention it was generally ignited by the propagation of an ignition flame from an igniter compound contained within a plastic cup supported within the flared portion of the nozzle venturi. The base of this igniter cup is provided with concentric rings of electrically conductive material to which the leads for the electric squib are connected. These rings are supposed to make contact with spring fingers extending into the projector when the rocket is loaded therein, but frequently poor electric contact is made. Non-uniform ignition is obtained since the propagation of the ignition flame is in a direction opposite to the gas flow, delaying the ignition of the propellant in the forward portion of the ignition chamber and producing non-uniform burning of the propellantthroughout the total burning time.

The advantages of an igniter disposed forwardly in the combustion chamber have been known for some time, and various igniter designs permitting forward ignition have been proposed by those working in the art, but most'of'these ideas have been difiicult to put into practice. Furthermore, these igniters which are supported in the forward portion of the chamber have to be inserted when the propellant and projector are assembled, with the result that hazards of premature ignition are increased.

A principal object of this invention is to provide an igniter which may be inserted through the nozzle of the rocket and which will he between the burster tube and the powder charge.

Another object of the invention is to provide a new and improved method for making the electrical connections necessary for conducting the firing current to the electric squib of the conductor.

A further object of the invention is to provide an igniter casing of suflicient flexibility in one direction to allow the casing to bend around the burster tube and the powder grains, having at the same time sufilcient rigidity to allow insertion from the nozzle.

Still further objects of the invention are to provide means for securing the igniter tube within the combustion chamber; means for sealing the container for the igniter compound against possible moisture intrusion; and to provide means for retaining the lead wires of the igniter within the chamber after the igniter casing has been filled and prepared for use.

Original experiments in designing an igniter casing for this invention comprised the use of a strip of plastic material wound spirally. It was found that such a container was not sufllciently flexible and was not easily insertable from the nozzle end. It was found that a container. of elliptical cross-section did have the necessary flexibility in one direction, and at the same time maintained sufficient rigidity in another direction so that the igniter could be easily inserted.

It was necessary to design means to secure the igniter within the chamber after it had been inserted through the nozzle, and we conceived the idea of utilizing a plastic disc and securing the igniter container to a projection therefrom. The electric wires from the squib were brought out through holes formed in this projection and were sealed thereto by filling the inside of the projection with any suitable sealing compound, such for example as that known as Glyptalf 'I he recess for the screw which secures the disc to the rod was also sealed with compound to completely seal the igniter from any possible moisture intrusion. Extension leads for the squib were provided, and the plastic disc was provided with a recess in its surface wherein these extension leads were conveniently coiled. and they are retained in place in their coiled position by a cardboard disc which fits into another recess in the plastic disc and which is removed when the rocket is inserted in the projectile tube, allowing the leads to be uncoiled, the retaining clip to be removed, and each lead connected individually to a suitable clamp on the projector. Thus the igniter compound may be easily inserted through the nozzle so as to lie adjacent the powder grainsv at the forward end of the combustion chamber.

Other objects and advantages of the invention will become apparent duriiig the course of the following specification, and the accompanying drawmgs, forming part of the specification, wherein like numbers are used to designate like parts.

In the draw hgs Figure 1 is a fragmentary view in longitudinal section taken on e l-l of Figure 2 of a rocket motor employing an igniter assembly of this invention,

Figure 2 is a cross sectional view taken on line 2-2 of Figure 1, and,

Figure 3 is a cross sectional view taken on line 3-3 of Figure 1.

Referring in detail to the drawings, the numeral 5 designates a rocket motor combustion chamber which has a forwardly flared end leading to a constricted throat 6 from which the flared sides of the nozzle 7 extend to provide for the discharge of the expanded gases of combustion therethrough. The propellant consisting of a plurality of cylindrical powder grains 8, each of which has a single axial perforation 9 formed therein. These grains are supported to lie lengthwise of the motor chamber 5 by being strung on a. plurality of trap rods l and are restrained within the chamber by a trap ring H whichis welded to each of the trap rods I0. The burster tube 12 is shown extending longitudinally of the combustion chamber.

The rocket motor chamber 5, as shown in Figure 1, is provided with a movable insert which is designed to provide an automatic self-adjustment of the pressure within the combustion chamber, the said insert being more fully described by one of the co-inventois of this invention in application Serial No. 583,140 filed March 16, 1945. The insert assembly consists of a 3-vane spider I3 which is inserted into the rocket motor chamber from the end thereof opposite the nozale 1. The spider l3 retains the rod I 6 centrally within the nozzle venturi. The rod 8' is provided with a forward portion of reduced cross-section and a rear portion of enlarged diameter! The insert l5 which is supported on the rod is a streamlined configuration and moves rearwardly at pressures exceeding a predetermined maximum, to move down the rod M to the diameter of its forward position.

The rod M is conveniently used for retaining the insulated disc it within the end portion of the nozzle 1. The disc 16 has a projection ll formed on its surface which is elliptical in a cross-section and has an opening [8 drilled therethrough through which extend the lead wires l9 and 20 of an electrical squib 2|.

An elliptical shaped container 22 formed of an extruded plastic material has its open end 23 fitted over the projection I1. A partition member 24 is disposed within the container 22 for retaining black powder 2-5 or other suitable igniter composition in the forward end thereof.

The outer surface of the insulated disc I6 is provided with a circular recess 26 into which the lead wires l9 and 20 of the electric squib 2| are coiled. The two ends of these leads are brought together and clipped so that they may at all times provide an eifective short circuit of the electric squib 2|. A cardboard disc 21 is retained in the insulated disc l6 by being inserted into a cut-out portion 28 thereof and serves to retain the coiled wires l8 and 20 within the circular recess 26. The cardboard disc 21 is provided compartment having a closed end with a tab 29 which permitsits easy removal to gain access to the said coiled extension leads.

In use, the propellant and rocket motor chamber are assembled for shipment as a unit without the igniter in place, and thus the hazards of transporting the rocket with an assembled igniter may be avoided. The igniter assembly is transported separately, and is inserted into the motor chamber just before the rocket is loaded into the projector tube. The cardboard disc 21 is then removed and the extension leads are unclasped and connected to suitable clasps provided on the projector for completing an electrical circuit leading to the electrically fired squib 2|.

As shown in Figure 1, the recess 30 formed in th projection I1 is filled with sealing compound 3| to seal the lead wires l9 and 20, and the recess 32 for the screw 33 which secures the disc l6 to the rod I 4 is also filled with sealing compound M.

It is to be understood that vention herewith shown is to ferred example of the same, and that various -modifications may be made in the combination and arrangement of parts disclosed in the drawings accompanying the invention without departing from the spirit thereof as defined in the claims annexed hereto.

Having thus described our invention, we claim:

1. In combination a rocket motor supported by a "pay-load compartment at its forward end, said motor comprising a cylindrical combustion chamber, a plurality of trap rods extending longitudinally of said chamber, a cylindrical grain of propellant material having a cylindrical and concentric perforation strung on each of said rods, a tube communicating with said pay-load" extending longitudinally and concentrically of said chamber, a constricted orifice formed in the chamber at the end opposite said pay-load" compartment for the high velocity discharge of the production of combustion liberated by said propellant, a flared exit passage extending from said the form of the inbe taken as a preconstricted orifice for expanding said combustion products to increase the exit velocity theregf, an igniter for said propellant comprising an elongated plastic envelope of generally elliptical crosssection containing an igniter composition, and having flexibility for insertion in said chamber through said constricted orifice to lie between said propellant grains and said tube, and a closure disc for said flared exit passage supporting said envelope.

2. In combination a. rocket motor supporting a pay-load" compartment at its forward end, said motor comprising a cylindrical combustion chamber, a multigrain propellant supported within said chamber so that the grains lie generally longitudinally thereof, a constricted exit orifice at the end of said chamber opposite said payload for the discharge of combustion products liberated by said propellant, a rearwardly flared exit passage extending from said constricted orifice for expanding said combustion products to increase the exit velocity thereof, an igniter for said propellant including an envelope containing an igniter composition and an electrical ignition means therefore, a closure disc inserted within said flared exit passage, ignition leads extending from said means through said disc, said 'lisc having a recess formed therein, and removable means retaining said leads coiled within said recess, said envelope comprising an elongated plastic tube of generally elliptical cross-section anemone the direction or its minor axis only whereby said envelope may be inserted into said chamber through said orifice.

- BERT A. APPIETON.

CLARENCE N. HICKMAN. CAROLD 1"..BJORK.

REFERENCES CITED The following references are of record in the file of this'patent:

UNITED STATES PATENTS Number Name Date 1,380,602 Van Deuren Nov. 30, 1920 1,170,815 Eroe Aug. 29, 1939 10 2,404,190 Pope July 16, 1946 FOREIGN PATENTS Number Country Date Great Britain June 24, mos 

